Portable stapler with pneumatic drive and return



A. G. JUILFS Sept. 5, 1967 PORTABLE STAPLER WTTH PNEUMA'IIC DRU/E ANDRETURN E Sheets-Sheet 1 Original Filed April 27 1959 Sept- 5, 1967 A. G.JUILFS FGRTABLIS STAPLEH WITH PNEUMATC DMVE AN!) RETURN Original FiledApril 27, 1959 E Sheets-Shel r' x Z?) D C INVENTOR.

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United States Patent Oilce Re. 26,262 Ressuecl Sept. 5, 1967 26,262PORTABLE STAPLER WITH PNEUMATIC DRIVE AND RETURN Albert G. Juilfs,Anderson Township, Hamilton County, Ohio, assigner to Senco Products,Inc., Fairfax, Ohio, a corporation of Ohio Original No. 2,983,922, datedMay 16, 1961, Ser. No. 809,129, Apr. 27, 1959. Application for reissueMar. 24, 1966, Ser. No. 544,639

19 Claims. (Cl. 227-130) Matter enclosed in heavy brackets appears inthe original patent but forms no part of this reissue specification;matter printed in italics indicates the additions made by reissue.

This invention resides in the provision of a power operated device inwhich fluid power is used both to actuate a piston on a work performingstroke and also to return the piston in preparation for a succeedingstroke, all with a minimum use of fluid power, means other than uidpower being used to hold the piston in pre-work stroke position.

An important object of this invention is to provide a stapler in whichair is utilized both to drive a piston from an initial position for adrive stroke and to effect return of the piston substantially to itsinitial position, whereafter the piston will be held in such initialposition by means other than air and the air will not be used tomaintain the driver in such initial position.

Another imp-ortant object of this invention is to provide a portablestapler with means for storing air as the staple driver and itsactuating piston move in a staple driving direction in such a mannerthat the air thus stored on the driving stroke may be used to aid returnof the driver and piston for the next driving stroke.

A further object of this invention is to provide a portable staplerwhich uses a minimum amount of air even though the driver actuatingpiston is both driven and returned by air.

A very important object of this invention is to provide an air operateddevice in which a piston is both driven and returned by air without theneed for or use of a return spring for the piston.

Another important object of this invention is to provide an air operateddevice in which a piston is reciprocated in a cylinder by air pressurealone rand wherein the length of the cylinder is kept t-o a minimum.

A specific object of this invention is to provide a portable penumaticstapler in which a piston and driver are air actuated to drive a stapleand in which the driver and piston are returned without a driver returnspring, all with the use of a minimum amount of air.

Another specific object of this invention is to provide a portablepneumatic stapler in which the height of the stapler (the distance fromthe tip of the staple discharge nose to the top of the cylinder) isequal to or less than that of comparable staplers in which a spring isused to return the piston and driver, and in which this stapler heightis markedly less than that of other comparable Staplers in which thepiston and driver are returned by arr.

A very important object of this invention is to provide a relativelysmall portable pneumatic stapler which may be used on production linework to do the same jobs now performed by larger tools, which novelsmall stapler is substantially trouble free and extremely economical tooperate.

These and other objects of this invention will become apparent to thoseskilled in the art from a reading of the description to follow and froman examination of the accompanying drawings, in which drawings likenumerals are employed to designate like ports throughout and in whichthe invention, for purposes of illustration, is shown as applied to aportable pneumatic stapler.

FIGURE 1 is a cross-sectional view of the stapler embodying thisinvention, the section being taken on the line 1-1 of FIGURE 4,

FIGURE 2 is a fragmentary sectional view showing the position of certainof the driving mechanism during the driving stroke,

FIGURE 3 is a further fragmentary cross-sectional view showing adifferent stage in the driving stroke and indicating also a possiblemodification,

FIGURE 4 is a front view of the stapler embodying this invention,particularly as seen from the left hand side of FIGURE 5,

FIGURE 5 is a side elevation, with parts broken away and parts insection, of the stapler embodying this invention,

FIGURE 6 is a top view of the stapler shown in FIG- URE 5,

FIGURE 7 is a side elevation, with parts broken away and parts insection, of a modification of the invention,

FIGURE 8 is a fragmentary side elevation, with parts broken away andparts in section, of another modification of this invention,

FIGURE 9 is a fragmentary top View of the modification shown in FIGURE8,

FIGURE l0 is a fragmentary sectional view showing one of the forms ofthis invention,

FIGURE 11 is a fragmentary sectional view showing another of the formsof this invention, and

FIGURE 12 is a fragmentary sectional View showing a further modificationof this invention.

Although the invention is herein shown and described as applied toportable pneumatic staplers, it is to be understood that in its broadestaspects the invention is not to be so limited except as particularly setforth in the claims appended hereto.

Broadly stated, this invention comprises driving a piston by fluid powerfrom a retracted position within a cylinder to a piston travel limitingmeans, returning the piston to its retracted position by fluid powerapplied in the region of said travel limiting means, and releasablyholding the piston in retracted position by means other than fluidpower. This may be accomplished by using a source of fluid power toovercome the releasable holding means and to drive the piston from itsretracted position to the travel limiting means, diverting the source ofuid power to return the piston to its retracted position while relievingthe piston from the initial inuenee of the fluid power used on the drivestroke, and holding said piston in retracted position by said releasablemeans While relieving the piston from further influence by the fluidpower used on the return stroke.

In order to minimize the uid power diverted for the return stroke it isvpreferred to provide a reservoir or storage chamber into which fluidmoved by the piston on its drive stroke is forced. The fiuid powerdiverted for the return stroke is used to supplement that stored in thereservoir and thus only la very small amount of fluid need be sodiverted. In this way fluid which in other arrangements is simplyexhausted on the drive stroke of the piston is utilized to aid thereturn of the piston. And when the piston is returned, means other thanfluid power are employed to hold the piston in retracted position, thuseffecting ra further saving in the fluid used.

Applying these principles to stapling, particularly to portablepneumatic Staplers, `a satisfactory stapler utiliz ing this inventioncomprises a cylinder in which a piston is reciprocable and a drive trackin which a staple diver is reciprocable. The driver is attached to thepiston. There are releasable holding means to hold the piston in aretracted position and a suitable stop or travel limiting means to whichthe piston is driven when the holding means is overcome. Conventionalmeans are provided for placing a succession of staples in said drivetrack in position to be engaged by said driver and driven through saidtrack into work when said piston moves on its drive stroke. The pistonis moved on its drive stroke by air from a source ot' compressed airintroduced in the region of said releasabie holding means. After saidpiston is thus driven to its said stop compressed air is no longerintroduced in the region of said releasable holding means. The region ofthe cylinder above the piston is open to exhaust and compressed air isintroduced below said piston in the region of said stop. This returnsthe piston to retracted position and engagement with said releasableholding means. In the retracted position of said piston the region ofthe cylinder below said piston is open to exhaust and compressed air isno longer introduced in the region of said stop.

Preferably there is a definite exhaust passage through which air maypass from beneath the piston when the piston is in its retractedposition. In the preferred form of the invention a storage chamber orreservoir is provided and this reservoir communicates with that end ofthe cylinder in which the stop is located. Immediately after the pistonis moved from its releasable holding means the exhaust passage isclosed. Air moved by the piston on its drive stroke is thus forced intothe reservoir rather than exhausted. Also preferably, upon the pistonreaching its stop a small amount of compressed air is added to thatstored in `the reservoir. When the air above the piston is opened toexhaust, the compressed air in the reservoir is sucient to return thepiston. When the piston is returned the exhaust passage is opened andcompressed air is no longer introduced in the reservoir. Air remainingin the reservoir and lower part of the cylinder exhausts through saidpassage. The piston is held by the reletasable holding means until airis again introduced in the region of said holding means to initiateanother cycle.

Before proceeding with a more detailed description of the invention afew observations are in order. It would be possible to eliminate theexhaust passage as such, primarily under two conditions. One, if thelower end of the cylinder and drive track in the region of the stop weremade with sloppy clearances, the stapler would operate satisfactorilyalthough less air would be stored and more would be wasted. Two, if thelower end of the cylinder and drive track in the region of the stop weremade relatively tight, the stapler would operate fairly satisfactorilyif not tired too rapidly; with no exhaust passage and a tight t therewould be a gradual build up of air which would eventually prevent properstaple driving, unless operation was slow enough to permit adequateleakage. Also, the reservoir as such-in the invention as broadlyconsidered-could be eliminated and compressed air introduced directlyunder the piston when at its stop, although this would result in greaterair loss.

Referring now [particular] parrcularly to FIGURE l of the drawings thestapler is illustrated as including a handle section 2l, a main body 22and a nose section 23. A portion of the means for feeding a successionof staples into the nose section 23 is generally indicated at 24. Thestaple feed means is conventional and does not form a part of thisinvention; there are several satisfactory staple feed means availablefor this purpose.

The handle 21 includes a large `air chamber 25 and a conventionalconnection 26 to a suitable supply of air under pressure.

Fixed within the main body 22 is, in this form of the invention. asleeve 27 which has a threaded portion 28 near its upper end whichengages the internal threads 29 at the upper end of the body section 22.The sleeve 27 is screwed into the body section 22 until the lower endcomes to rest on the shoulder 30 provided in the lower end of the mainbody section 22. Mounted in the lower end of this main body section 22is a resilient bumper 31 which is relieved about its periphery asindicated at 32. The upper end of the main body section 22 is closed bya cap 33 having suitable threads to engage the threads 29. The cap 33has a sleeve 34 fixed thereto and within this sleeve there is secured amagnet 3S. Preferably the magnet 35 extends slightly below the loweredge of the cap 33 and particularly of the sleeve 34.

Slidably mounted within the cylinder sleeve 27 is a metal `piston 36 towhich is firmly secured a staple driver 37. Preferably the driver 37 isconnected to the piston 36 by means of a pin 38. Also it is preferredthat the piston 36 be cup-shaped and filled with a hard, tough but lightand resilient material 39. This material is relieved at 40 so that thedriver may have some lateral movement or wobble on the pin 38.

This lateral movement insures that the driver 37 will not bind in thedrive track 41 `provided in the nose section 23.

In the form of the invention illustrated in FIGURE 1 there is an airstorage chamber 42 defined by the cylinder sleeve 27 and main bodysection 22. Ports 43 in the lower end of the sleeve 27 communicate withthis charnber 42. These ports are open. Also located in the sleeve 27are one or more other ports 44 which are normally closed by resilientmeans 45. Each of these ports 44-45, therefore, constitutes a one-way ornon-return valve.

The piston 36 and pinned driver 37 are actuated by air which iscontrolled by valve means now to be described, The particular valvemeans shown are the subject matter of another application for patentiled by this inventor of even date herewith and entitled Remote ControlAir Valves, Serial No. 819,387. Insofar as the instant invention isconcerned this particular valve mechanism is not critical. Any workablevalve mechanism which will introduce air under pressure about the piston36 will suffice. For the sake of completeness, however, a briefdescription of the valve mechanism shown follows. It is to beunderstood-and emphasized-however, that the instant invention--thesubject matter of this applicationis directed to the means for returningthe piston and driver by air and maintaining them in proper pre-driveposition by means other than air.

A trigger 46 is hingedly fixed to the stapler as indicated at 47. Thistrigger normally lies adjacent a valve button 48. The button 48 isnormally spring biased to a position in which it prevents air frompassing through the orifice 49 to the passage 51. There is a passage 50leading from the chamber 25 to the remote control valve chamber 52.

Also in the handle of the gun is a tiring valve cylinder 53 and a pairof closure plugs 54 and 55. A trigger piston 56 is slidable in the valvecylinder 53. The plug 54 is relieved so that air which eventually cornesthrough the passage 51 will get into position behind the piston 56 anddrive it upwardly as viewed in FIGURE 1. Also within the firing valve 53is an elongated valve stem 57 having fixed thereto a valve member 58adapted to seat on the valve seat 59. A passage 60 leads from the airchamber 25 to the upper region of the tiring valve cylinder 53. Apassage 61 leads from the central region of the ring valve cylinder 53to an annular area or clearing 62 surrounding the upper part of thesleeve 27 and the piston 36. Since the diameter of the piston 36 isgreater than that of the magnet 35, and since the magnet 35 extendsbeyond the sleeve 34 and upper cap member 33. air entering the area 62may easily corne into contact with the top of the piston 36 in order tostart it on its driving stroke as will be described more fully shortly.

There is an exhaust tube 63 which extends through the handle 21 andchamber 25 thereof. This tube 63 communicates with an exhaust passage 64leading from the central region of the ring valve cylinder 53. Nestingwithin the trigger piston 56 is a valve member 65.

It will be observed that normally there is a clearance between the lowerend of the valve stem S7 and the bottom of a recess in the valve member65 which is approximately equal to the width of the passage 64.

FIGURE 1 illustrates the position of the stapler and its componentsprior to the time the trigger 46 is actuated. In this position any airin the clearance 62 is open to exhaust through the passage 61, aroundthe valve stem 57, through the passage 64 and out the end of the staplerhandle through the tube 63. Air entering the stapler into the chamber 25can go no further than the upper region of the tiring valve cylinder 53,via the passage 60, since the valve seat 58 will be seated on the seat59. The piston 36, and driver 37 which is pinned to it, will bemaintained in the upper portion of the cylinder defined by the sleeve 27by reason of the magnet 35.

Referring now particularly to the lower part of FIGURE l it will beobserved that the nose structure 23a is provided with an orifice 66which communicates with the drive track 41 ahead of the lower end of thestaple driver 37 and with a suitable clearance or passage 31a in thebumper 31. Thus it will be observed that when the piston 36 is againstthe magnet 35 air below this piston, within the cylinder defined by thesleeve 27 is open to atmosphere through the passage 31a, orifice 66 anddrive track 41. Any air within the storage chamber 42 is also free toexhaust through this same route.

The operation of the embodiment of the invention illustrated in FIGURE 1is as follows. The operator will grasp the handle 21 and squeeze thetrigger 46 thereby moving the valve button 48 so as to open the passage49 and permit air within the chamber 25 to pass through the passage 50,oriiice 49 and passage 51 to the clearance provided in the member 54behind the trigger piston 56. 'The trigger piston 56 will rise, takingthe valve button 65 with it. Initial movement of the button 65 serves toclose the exhaust passage 64. Further movement of the piston 56 andbutton 65 will result in upward movement of the stem 57 and valve member58. In this manner air is permitted to flow through the valve cage-theupper portion rof the firing valve cylinder 53-with the result that airwill pass from the chamber 25, through the passage 60, beneath themember 58 and around the stern 57, through the passage 61 to theclearance 62. This air ow is proportional to the movement of the triggervalve.

A delay is caused by the magnet which is holding the piston 36 in its upposition. When suicient pressure is obtained in the area 62 around thetop of the piston 36 to overcome the power of the magnet, the mainpiston starts to descend. By this time the trigger valve is full openand the gun is operating on full pressure.

As the piston is driven downward, the driver 37 closes the exhaust port66 in the nose member 23a which, with the member 23, defines the drivetrack 4l, while the air which is under the piston 36 is forced throughthe lower ports 43 in the sleeve 27 and is slightly compressed in thestorage chamber 42.

When the piston 36 reaches the end of its downward stroke, at whichpoint it will abut the bumper 31, the ports or one-way valves 44-45 inthe central part `of the sleeve 27 will be forced open by thepressurized air on top of the piston. In this manner, additional air iscompressed into the storage chamber 42. As seen in FIGURE 3 the valves`44e45 are preferably located so that they will be just above the piston36 when it is at rest on the bumper 31.

It will be readily understood by those skilled in the art that as thepiston 36 moves from its position adjacent the magnet 35 to the bumper31, the driver 37 moved through the track 41, engaged a staple Spositioned in the track by the feed means 24, and drove it through theend of the nose structure 23 into the work.

When the trigger 46 is released the spring biased valve button 48 willreturn to its closed position as indicated in FIGURE 1, whereupon airliow to the trigger piston 56 through the passages 50 and 51, andorifice 49, is shut off. The pressurized air under the trigger piston 56is released back through the remote valve and exhausted through groovesin the housing of this valve. These grooves, not shown, communicate withthe passage 51 when the button 48 is in its released position and suchgrooves are blocked by this button when it is moved to actuate thetiring valve. The detail of this is shown in my said copendingapplication.

The valve member 58 then abuts against its seat 59 thereby shutting offair ow to the main bore-the upper part of the cylinder sleeve 27. Thepressurized air which is in the cylinder above the piston 36 travelsthrough the passage 61 and forces the valve button 65 down past theexhaust port 64 and thus is exhausted through this port and the tube 63.

As the pressurized air on top of the main piston is exhausted, thevalves 44-45 on the central part of the cylinder sleeve 27 will close.The compressed air in the chamber 42 then expands through the lowerports 43 in the sleeve 27 and forces the piston 36 upwardly towards themagnet 35. When the main piston is almost at its upper position adjacentthis magnet 35, the lower end of the driver 37 will open the exhaustport 66 which `communicates with the drive track 41 and the compressedair under the piston 36 then exhausts. The momentum gained by the piston36 from the expansion of the compressed air, coupled with the pull ofthe magnet, causes the piston 36 to return to its original position.

The positions of various of the stapler parts during the above describedcycle of operation are shown in further detail in FIGURES 2 and 3. InFIGURE [3] 2 the parts are shown during an intermediate stage in thedriving stroke ofthe piston 36 and driver 37. It will be understood thatair is coming through the passage 61, as indicated by the arrow in thisligure, and having built up in the clearance 62 sutiicient to start thepiston 36 on its downward stroke and move it from the magnet 35, it isnow acting full force behind the piston 36 during this driving stroke.The staple driver 37 has moved sufficiently far to block the orifice 66leading to the track 41 and has engaged a staple S and started to moveit through this track in the nose members 23-23a. Air beneath the piston36, which cannot escape through the track 41 at this time, is forcedthrough the ports 43 into the storage chamber 42 and this is alsoindicated by arrows in this figure.

Although FIGURE 3 also shows a modication of the invention, which willbe described, it does show the position of the main driving componentsat the time the piston 36 and driver 37 have reached the end of theirdriving stroke. In this position the piston 36 has seated against itsstop 31 and has cleared the valve-ports 44. These ports are normallyclosed by resilient member 45. When the piston 36 has reached theposition of FIGURE 3 the air pressure above this piston is sufficient tomove the resilient member 45 so as to open the ports 44 whereuponadditional air is compressed in the chamber 42. FIGURE 3 alsoillustrates certain of the purposes of the clearance 32, or relief,given the stop 31. It will be observed that the ports 43 are located soas to communicate with this clearance area. The piston 36 has a greaterdiameter than the relieved portion 32 of the stop 31. Thus, upon returnof the piston 36 as above described, it will be seen that such return isaided by reason of the fact that the air compressed within the chamber42 has an opportunity to act on the lower side of the piston 36 whichextends beyond the relieved bumper 31.

In FIGURE 10 I have shown the arrangement of the valve ports 44 andresilient closure 45 in greater detail. In this figure it will beobserved that there are four ports 44 located in a row in the wall ofthe sleeve 27. A bead 67 is provided in the region of these ports on theoutside of the sleeve 27. A groove 68 is provided in this bead orenlarged portion of the sleeve 27 and a band of resilient material 45 islocated in this groove 68. The material 45 is selected so that the airpressure is sufficient to move the material in the groove so as to passthrough the port 44 into the chamber 42 in the manner described.

It will be apparent that modifications may be made in this inventionwithout departing from its scope and spirit. Some of thesemodifications, by way of example, are disclosed herein.

Referring now particularly to FIGURE 3, there is illustrated anothermeans for maintaining the piston 36 in its up position, this other meansto replace the magnet 35 described in connection with the embodiment ofFIG- URE l. Preferably the cap 33 has been enlarged and provided with asmall projection 69 against which the piston 36 will abut in its upposition. This will insure that air from the area 62 will reach the topside of this piston. The piston holding means comprises a ball detent7l] spring biased within a plug 71 screwed into the main body 22. Theball 70 is urged towards the interior of the cylinder sleeve 27 by thespring 72 and is restricted by the opening 73 which is somewhat smallerthan the diameter of the ball 70.

The detent means just described is located so as to register with thepin 38 by means of which the driver is held to the piston. Thus when thepiston 36 has been moved against the projection 69 the detent ball 70will be in alignment with the pin 38. One end of this pin is dished asindicated at 74 so that the ball 70 may be forced into engagement withthe dished end of the pin whereby to maintain the piston 36 in its upposition. When sufficient air pressure has built up on top of the pistonto overcome the spring 72, the ball 70 will retract as the piston startsits driving stroke. When the stored and compressed air from the chamber42 drives the piston to the projection 69 the detent ball 7l] willengage the end 74 of the pin 38 and hold the piston 36 in position whilethe air beneath the piston is free to exhaust through the orifice 66 anddrive track 41 as before.

Referring now particularly to FIGURE 12 there is illustrated yet anothermeans for holding the piston in its up position. In this arrangementthere is provided a spring clip 75 which extends through an orifice 76in the nose member 23 and into the drive track 41. The clip is sopositioned that when the stored and compressed air from the chamber 42returns the piston 36 to its up position, the clip will project into thedrive track 41 beneath the lower end of the driver 37 and thus maintainthe driver and piston in such up position. Again, when the air pressureabove the piston 36 builds up sufficiently to overcome the spring clip75 it will be forced out of the track 41 into the orifice [75] 76 andthe piston and driver will complete the driving stroke through the track4l.

lt will be apparent to those skilled in the art that releasable meansother than the magnet 35, detent 70 or clip 75 (for example, a suctioncup) may be used to hold the piston 36 in its up position without theuse of compressed air for this purpose. The elimination of air for thispurpose is a very important feature of the invention. Those staplerswhich depend on compressed air to maintain the piston 36 in the upposition consume a great deal of air and are not economical to operate.In the preferred arrangement of this invention a small amount of air isstored (in other known tools this air is exhausted, wasted) andcompressed and then used to aid return of the piston to its homeposition at the top of the cylinder. Upon reaching this position,however, releasable mechanical means are employed to hold it in positionuntil another drive stroke is initiated. During such holding time no airis required and in this manner a big saving in the economics of stapleroperation has been accomplished.

Another important advantage of the present invention is the eliminationof return springs for the driver and/or piston. By returning the pistonto home position by air, a return spring has been eliminated. Returnsprings in the past have eventually always caused some trouble and it isa distinct advantage to be able to eliminate them. In this invention notonly is the return spring eliminated and the driver and piston returnedby air, but also a great saving in the amount of air needed has beeneffected by the novel arrangement of storing and compressing arelatively small amount of air, which would otherwise be wasted anyway,and which small amount of air has only to return the piston to homeposition whereafter the piston will be maintained by means other thanair.

It should be emphasized that the elimination of the return spring has atleast one other important advantage. Those staplers which usepisto-n-driver return springs must provide space or room for collapse ofthe spring on the drive stroke. This usually requires a stapler having alonger cylinder. This means the height, i.e., the distance from the tipof the staple discharge nose 23 to the top of the housing 22, of thestapler must be increased. A larger tool results-one which is heavier,harder to manipulate and requires more air to operate.

An even more striking comparison illustrating advantages of the[intsant] instant invention takes place when one compares the air returntool of this invention with those heretofore known. The prior art airreturn tools utilize two pistons and require, in effect, a cylinder foreach. The tool of this invention, therefore, which tool uses one pistonand one cylinder-and no return spring-obtains the same or equivalentoperative drive stroke for the piston in a cylinder about one-half thelength required by these other two piston air return Staplers. Thus asmaller tool capable of accomplishing the same jobs as these otherlarger tools is achieved by this invention. This means a saving inmaterial of manufacture, air for operation, and a tool which is easierto handle.

The specific, preferred form of the invention has been described asincluding `a storage area or reservoir. In FIGURE 1 this is illustratedat 42 and is defined as the area between the main body 22 and cylindersleeve 27. This has been found to be a very satisfactory arrangement butit is not the only one possible. It will be apparent to those skilled inthe art that this storage chamber may take other forms and be located inother places. Examples of this are illustrated and will now bedescribed.

Referring now particularly to FIGURE 7 the storage chamber 42a has beenplaced, for convenience, immediately above the staple feed mechanism 24.In this embodirnent of the invention there is a cylinder 27a in whichthe piston and driver reciprocate. This cylinder 27a has a port 43alocated adjacent the top of the bumper 31 and communicating with thechamber 42a, which chamber may be formed as part 22a of the main body orhousing 22. It will be understood that the chamber 42a may be extendedas indicated at 42h to a position wherein auother one-way valve port44-45 may be located in the cylinder 27a and through which air underpressure may pass when the piston 36 seats on the stop 3l, as describedin connection with FIGURE 1. Thus, as before, as the driver and pistonmove on the driving stroke air will be forced into the chamber 42a fromthe cylinder 27a through the orifice 43a. When the piston seats on thestop 3l, additional air under pressure may pass into the chamber 42a viathe passage 42b which communicates with one or more ports 44-45 asearlier described.

In the arrangement of FIGURE 7 it will be understood that the air storedand compressed into the chamber 42a will be sufficient to return thedriver and piston to the up position, whereafter the lower part of thecylinder will again be open to atmosphere and mechanical means such asthe magnet of FIGURE 1, the detent of FIGURE 3 or the clip of FIGURE l2will maintain the piston in such up position until another drive strokeis commenced.

In FIGURES 8 and 9 yet another manner of locating the air chamber isillustrated. In these figures the chamber is shown as comprising a tube42e fixed to the outside of the main body 22. The cylinder in which thepiston reciprocates is indicated at 27b and the stop for the piston isindicated at 31. The lower end of the storage tube 42e communicates witha passage 77 which passage in turn is open to the orifice 43b in thecylinder wall 27b. Again it will be understood that the passage 77extends to a position so that it communicates with a valve port 44-45located in the cylinder wall 27h so as to be just above the top of thepiston 36 when it is seated on the stop 31. In this manner additionalair under pressure moves into the reservoir tube 42e via the non-returnvalve 44-45 and the passage 77. The operation is as before; on the drivestroke of the piston and driver air beneath the piston is forced intothe storage tube 42e through the orice 43b and passage 77. When thepiston seats on the stop 31 additional air under pressure enters thetube 42e through one or more valve ports 44-45 communicating with thepassage 77. In all of these arrangements, illustrating preferred formsof the invention, the lower end of the stapler will be closed toatmosphere immediately after the piston commences its drive stroke, andwill be open to atmosphere when the piston is returned to its retractedposition adjacent the cap 33 by the relatively small amount of storedand compressed air within the particular storage chamber involved.

Thus far, in describing the preferred forms of this invention, thepassage or orice 66, which connects a definite clearance 31a in thetravel limiting means 31 with the drive track 41, has been included. Itis this orice which the driver 37, when the piston 36 moves from thereleasable holding means, closes, thereby insuring that most of the airmoved by the piston on its drive stroke will be forced into thereservoir rather than exhausted. And when the piston returns toretracted position the driver will open this exhaust means. There will,however, always be some leakage through the areas in which the driverreciprocates because the tolerances cant be held close enough to preventsuch leakage and not unduly impede the driver. It should here bementioned, therefore, that it would be possible to eliminate the passage31a, 66 as such and still obtain an operable tool. This would be done bymaking the clearances for the driver through the lower staplerelements-primarily the stop 31 and nose 23-generous or sloppy." Thiswould result in more of the air being exhausted-and less of the airbeing forced into the reservoir-on the drive stroke of the piston. Oncethe piston were seated on its stop, however, the piston wouldsubstantially block further exhaust and compressed air could be admittedto the reservoir. Upon release of air above the piston the air withinthe reservoir would return the piston as beforeexcept with a greaterexpenditure of air.

Also, it would be possible not only to eliminate the passage 31a, 66 butalso to make the tolerances as close as possible, thus reducing exhaustat all times to a minimum. This would result in more air being forcedinto the reservoir but it would lead to an undesirable build-up of airin the lower part of the stapler if the stapler were red rapidly. Thus,on attempted rapid fire under these conditions, the air, having nodefinite exhaust passage through which to exit and the clearances beingrelatively tight, would accumulate in the lower part of the stapler andeventually prevent or impede proper staple driving. (If the stapler wereoperated slowly, giving the air opportunity to leak out in spite of thetight fit, then staples could be driven even with the arrangement asdescribed; this would not ordinarily be commercially feasible.) Thus, itis desirable that there be some exhaust during such time as the pistonis in its retracted position for this insures that air will not build upunduly in the lower part of the cylinder, nor prematurely in thereservoir between each drive stroke of the piston.

The preferred form of the invention, therefore, envisions and embracesan arrangement wherein there is a definite exhaust passage which closesshortly after the drive stroke begins and opens shortly before thepiston reaches its retracted position, the clearances for the driverbeing otherwise relatively tight. In its broader aspects, however,deviations from this preferred arrangement, as above indicated, arepermissible.

In FIGURE l1 there is illustrated another embodiment of a suitable valvemeans by which compressed air may reach a storage chamber. In thisembodiment there is preferably a single orifice 44a which is normallyclosed by a valve member 45a made of resilient material and mounted on aspring 78 which urges it to close the orifice 44a. If desired additionalorifices of this type may be provided. The orifice 44a is located in thecylinder Wall 27 so that when the piston 36 is on its stop 31 air underpressure on top of the piston may force its way into the storage chamberby passing through the orifice 44a, the air pressure being suicient toovercome the spring 78. This, of course, is but another example of asuitable non-return or one-way valve which may be used in the practiceof this invention.

The preferred forms of this invention have so far been described, inconsidering the drawings, as including a storage chamber or reservoir.It has been pointed out that this reservoir may take different forms andbe located in different positions on the stapler. There has also beendescribed an arrangement in which, because of sloppyclearances-intentionally or unintentionally providedvery little air willbe forced into the reservoir on the drive stroke of the piston, althoughonce the piston is seated compressed air enters the reservoir sufficientto return the piston when the air above it is released. It is possible,therefore, to eliminate a reservoir into which air is forced on thedrive stroke of the piston, and still retain some of the advantages ofthis invention as broadly considered. Considering FIGURE 3, for example,all that would be needed would be a one-way valve for the port ororifice 43 to prevent passage of air on the drive stroke of the piston,some exhaust means for escape from the stapler of air moved by thepiston on the drive stroke, a connection between the orifice 43 and asource of compressed air, and valve or timing means to cause compressedair to enter beneath said piston when on its stop, such air passingthrough the orifice 43 and one-way valve provided for it; upon reachingits retracted position the piston would again be engaged by releasableholding means and air under the piston would be released. Such anarrangement, although using more air than the preferred forms, wouldstill retain such advantages as reduced stapler height and ease ofhandling.

In its broadest aspects, therefore, this invention may be considered asinvolving the combination of: releasable holding means, other than fluidpower, to hold the piston in retracted position; liuid power to overcomethe releas able holding means and drive the piston to a piston stop;means to release the uid power used to drive the piston to its stop;Huid power operable beneath said piston to return said piston to saidreleasable holding means when said rst mentioned fluid power isreleased; and means to release said last mentioned liuid power at aboutthe time said piston is engaged by said releasable holding means.

In its more specitic, but still somewhat broad aspects, the inventionresides in the provision of a pneumatic stapler including a piston and[driver] driver; releasable holding means, other than air, for holdingthe piston in a retracted position; means to introduce compressed air soas to overcome said holding means rand drive said piston to a pistonstop; a reservoir into which air is moved by said piston as it makes itsdrive stroke; means to introduce additionaland compressed-air into saidreservoir; means to release the air .above said piston so that the airin said reservoir will return the piston to its retracted position andre-engagement with the holding means; and means to exhaust the airbeneath said piston in retracted position; said exhaust means beingopened immediately before completing a return stroke. The form andlocation of the reservoir may vary. The releasable holding means mayvary. The type of exhaust means may vary. The manner of introducingadditional, compressed air into the reservoir may vary. All of this hasbeen described above.

It is believed that the operation of the stapler of this invention hasbeen sufficiently described in the above passages. Although theinvention has been described in connection with certain particularembodiments and structures, it is to be understood that the invention isnot limited to these particular embodiments and structures exceptinsofar as they are specifically set forth in the subjoined claims.

Having thus described the invention, what is claimed as new and what isdesired to be protected by United States Letters Patent is:

1. In a pneumatic stapling tool having a cylinder provided with a head,means for admitting air under pressure from a source of compressed airto said cylinder, a piston in said cylinder and a driver arranged to beactuated by said piston to travel in a driver slot to drive a staple,and means to place a succession of staples in said driver slot to bedriven by said driver; the improvement which comprises: releasable meansoperative independent of air pressure for normally holding said pistonin retracted position with a portion, at least, of the head of saidpiston exposed to compressed air admitted to said cylinder, and means tolimit the travel of said piston in a staple driving direction; a port insaid cylinder adjacent said travel limiting means and disposed justbelow the lower surface of said piston when said piston has abutted saidtravel limiting means, a reservoir connected to said port so as toreceive air moved by said piston when said piston is moved from itsretracted position to said travel limiting means, means to admitcompressed air into said reservoir only after said piston abuts saidtravel limiting means, and a clearance through said cylinder for airmoved by said piston in traveling from its said retracted position tosaid travel limiting means, said piston substantially closing saidclearance when said piston abuts said travel limiting means; wherebywhen compressed air is admitted to said cylinder said piston and driverare caused to move in a staple driving direction, and whereby when saidpiston abuts said travel limiting means and closes said clearance,compressed air is admitted into said reservoir and is caused to act uponthe lower surface of said piston via said first mentioned port, wherebywhen compressed air is no longer admitted to said cylinder, the airunder pressure in said reservoir causes said piston to return toretracted position where it is held independent of air pressure by saidreleasable means, excess air in said reservoir and said cylinderexhausting through said rst mentioned port and said clearance, saidclearance being more restricted than said 'first mentioned port wherebyair moved by said piston, when said piston moves from its said retractedposition to said travel limiting means, passes through said firstmentioned port into said reservoir.

2. The improvement of claim 1 in which the said compressed air admittedto said reservoir `after said piston abuts said travel limiting means isthe compressed air in said cylinder.

3. The stapling tool of claim 1 including means to substantially closesaid clearance immediately after said piston moves from its saidretracted position.

4. The stapling tool of claim 1 in which said clearance constitutes apassage which is through said travel limiting means to said driver slotjust beyond the end of said driver when said piston and driver are inretracted position, said passage being larger than required toaccommodate said driver, said driver substantially blocking movement ofair from said passage to said slot after said piston and driver movefrom said retracted position.

5. In a pneumatic stapling tool having a cylinder provided with a head,means for admitting air under pressure from a source of compressed airto said cylinder, a piston in said cylinder and a driver arranged to beactuated by said piston to travel in a driver slot to drive a staple,and means to place a succession of staples in said driver slot to bedriven by said driver; the improvement which comprises: a magnetoperative independent of air pressure for normally holding said pistonin retracted position with a portion, at least, of the head of saidpiston exposed to compressed air admitted to said cylinder, and means tolimit the travel of said piston in a staple driving direction; a port insaid cylinder adjacent said travel limiting means and disposed justbelow the lower surface of said piston when said piston has abutted saidtravel limiting means, a reservoir connected to said port, means toadmit compressed air into said reservoir only after said piston abutssaid travel limiting means, and a passage through said cylinder for airmoved by said piston in traveling from its said retracted position tosaid travel limiting means, said piston substantially closing saidpassage when said piston abuts said travel limiting means; whereby whencompressed air is admitted to said cylinder said piston and driver arecaused to move in a staple driving direction, and whereby when saidpiston abuts said travel limiting means and closes said passage,compressed air is admitted into said reservoir and is caused to act uponthe lower surface of said piston via said first mentioned port, wherebywhen compressed air is no longer admitted to said cylinder, the airunder pressure in said reservoir causes said piston to return toretracted position where it is held independent of air pressure by saidmagnet [releasable means], excess air in said reservoir exhaustingthrough said rst mentioned port and said passage.

6. In a pneumatic stapling tool having a Icylinder provided with a head,means for admitting air under pressure from a source of compressed airto said cylinder, a piston in said cylinder and a driver arranged to beactuated by said piston to travel in a driver slot to drive a staple;the improvement which comprises: releasable means operative independentof air pressure for normally holding said piston in retracted positionwith a portion, at least, of the head of said piston exposed tocompressed air admitted to said cylinder, means to limit the travel ofsaid piston in a staple driving direction, a port in said cylinderadjacent said travel limiting means and disposed just below the lowersurface of said piston when said piston has abutted said travel limitingmeans, a reservoir connected to said port whereby air below said pistonis discharged into said reservoir during staple driving movement of saidpiston, a second port in said cylinder also communicating with saidreservoir, said second port being disposed just above the head of saidpiston when said piston has abutted said travel limiting means; wherebyupon admission of compressed air to said cylinder, said piston anddriver are caused to move in a staple driving direction and the airbelow the piston is forced into said reservoir, until said piston abutssaid travel limiting means `and uncovers said second port, whereupon theair under pressure above said piston passes into said reservoir and iscaused to act upon the lower surface of said piston, whereby whencompressed air is no longer admitted to said cylinder and said cylinderis open to atmosphere, the air under pressure in said reservoir causessaid piston to return to retracted position where it is held independentof air pressure by said releasable means.

7. In a portable pneumatic stapler comprising a cylinder, a pistonreciprocable in said cylinder between a home position and a drivenposition, a driver connected to said piston, a drive track in which saiddriver reciprocates, means to feed a succession of staples into saiddrive track in position to be driven by said driver, and means foradmitting compressed air to said piston so as to move said piston fromsaid home position on a drive stroke to said driven position, whereby todrive a staple through said drive track into work, the improvement whichcomprises: releasable means to hold said piston in its home positionuntil said means for admitting compressed air to said piston isactuated; an air storage chamber; 'air conduit means connecting saidchamber with that end of said cylinder towards which said piston isdriven on its drive stroke; valve means to permit air between saidpistons home position and said pistons driven position, when said pistonis in its home position, to escape to atmosphere, said valve meansincluding means to prevent escape of air to atmosphere when said pistonleaves its home position; and an additional port to introduce compressedair into said chamber when said piston is in its driven position;whereby, when said piston moving means is deactuated and said cylinderin the region of said releasable means is open to atmosphere, the air insaid chamber returns said piston to said releasable means.

8. In a pneumatic stapler comprising a cylinder having an upper end anda lower end, a piston slidable in said cylinder, a staple drive track, astaple driver slidable in said staple drive track, said staple driverbeing attached to said piston, staple feed means for feeding asuccession of staples into said staple drive track in position to beengaged by said staple driver, the improvement which comprises: holdingmeans normally operative to maintain said piston at the upper end ofsaid cylinder, means to introduce air at said upper end of said cylinderunder sufficient pressure to overcome said holding means and drive saidpiston to the lower end of said cylinder whereby to drive said stapledriver through said staple drive track to drive a staple into work,valve means including said staple driver which opens said lower end ofsaid cylinder to atmosphere when said piston is maintained at said upperend of said cylinder by said holding means and which closes said lowerend of said cylinder to atmosphere when said piston is moved away fromsaid holding means towards said lower end of said cylinder byintroduction of air under pressure at said upper end of said cylinder,an air storage chamber which communicates with said cylinder at its saidlower end whereby air moved by said piston as it moves towards saidlower end of said cylinder is forced into said chamber, additional meansfor introducing compressed air into said chamber when said piston is atsaid lower end of said cylinder, said air in said chamber beingsufficient to return said piston to said holding means when air is nolonger introduced under pressure at said upper end of said cylinder, andmeans to exhaust air moved by said piston as it is moved towards saidholding means by the air from said chamber.

9. In a pneumatically operated device, a cylinder provided with a head,a piston slidable in said cylinder, releasable means operativeindependent of air pressure normally to hold said piston in a retractedposition, travel limiting means for said piston, means for admitting airunder pressure from a source to said cylinder so as to overcome saidreleasable means and drive said piston from said retracted position tosaid travel limiting means, a port in said cylinder adjacent said travellimiting means and disposed just below the surface of said piston whensaid piston has abutted said travel limiting means, a reservoirconnected to said port, a second port connected to said reservoir and toa source of air under pressure, a valve for said second port foradmitting air under pressure to said reservoir when said `piston abutssaid travel limiting means, the air under pressure in said reservoiracting upon the lower surface of said piston via said first mentionedport, and a passage from said cylinder for air beneath said piston whensaid piston is in its retra-cted position, said piston when seated onsaid limiting means acting to seal off said passage while air isadmitted to said reservoir through said second port, whereby when airpressure is no longer admitted to said cylinder and said air pressure isdiminished, the air under pressure in said reservoir causes said pistonto return to retracted position where it is held independent of airpressure by said releasable means, excess air in said reservoir andcylinder exhausting through said passage.

10. The device of claim 9 in which said passage is more restricted thansaid first mentioned port whereby air moved by said piston, when saidpiston moves from its said retracted position to said travel limitingmeans, passes through said first mentioned port into said reservo1r.

11. The device of claim 9 including means to substantially close saidpassage immediately after said piston moves from its said retractedposition.

12. The device of claim 9 in which said second port connects saidreservoir and said cylinder, said second port being positioned in saidcylinder so that it is exposed to air under pressure in said cylinderwhen said piston abuts said travel limiting means and seals said passageand the whole lower end of said cylinder.

13. The device of claim 9 in which said releasable means comprises amagnet.

14. In a pneumatic stapling tool having a cylinder provided with a head,means for admitting air under pressure from a source of compressed airto said cylinder, a piston in said cylinder anda driver arranged to beactuated by said piston to travel in a driver slot to drive a staple,the improvement which comprises: a magnet to hold said piston inretracted position with a portion, at least, of the head of said pistonexposed to compressed air admitted to said cylinder, means to admitcompressed air to said cylinder sufficient to overcome said magnet anddrive said piston, means to limit the travel of said piston in a stapledriving direction, a iirst port in said cylinder adjacent said travellimiting means, a reservoir connected to said first port whereby airbelow said piston is forced into said reservoir during staple drivingmovement of said piston, a second port in said cylinder alsocommunicating with said reservoir, said second port being disposed abovethe head of said piston when said piston has abutted said travellimiting means, whereby the compressed air in said cylinder above saidpiston then passes through said second port into said reservoir, andmeans to stop the flow of compressed air to said cylinder and to opensaid cylinder to atmosphere in the region of said magnet, whereby thecompressed air in said reservoir passes through said first port andreturns said piston to said magnet.

l5. The tool of claim 14 in which said rst port is disposed just belowthe lower surface of said piston when said piston has abutted saidtravel limiting means, a nonreturn valve for said second port, and aclearance opening the cylinder to atmosphere in the region of saidtravel limiting means, said clearance being more restricted than saidfirst port and said clearance being blocked by said piston when it abutssaid travel limiting means.

16. The tool of claim 15 in which said clearance is substantiallyblocked by said driver immediately after said piston leaves said magnet.

17. In a fluid-power operated device, a cylinder provided with a head, apiston slidable in said cylinder, a magnet to hold said piston in aretracted position, travel limiting means for said piston, means foradmitting fiuid under pressure from a source to said cylinder so as toovercome said magnet and drive said piston from said retracted positionto said travel limiting imeans, a rst port in said cylinder adjacentsaid travel limiting means, a reservoir connected to said first portwhereby fluid moved by said piston when said piston is driven to saidtravel limiting means is forced into said reservoir, a second portconnected to said reservoir and to a source of fluid under pressure, avalve for said second port for admitting uid under pressure to saidreservoir when said piston abuts said travel limiting means, the fiuidunder pressure in said reservoir acting upon the lower surface of saidpiston via said rst port, and means to diminish the l5 uid pressureabove said piston, whereby the uid under pressure in said reservoircauses said piston to return to retracted position where itis held bysaid magnet.

18. The device of claim 17 in which said second port is located in saidcylinder above said piston when said piston abuts said travel limitingmeans, said valve being a non-return valve, whereby the Huid underpressure admitted to said reservoir through said second port is thatfluid which served to drive said piston from the retracted position tosaid travel limiting means.

19. In a pneumatically operated device, a cylinder provided with a head,a piston slidable in said cylinder, releasable means operativeindependent of air pressure normally to hold said piston in a retractedposition, travel limiting means for said piston, the surface of saidtravel limiting means which contacts said piston being less in area thansaid cylinder, means for admitting air under pressure from a source tosaid cylinder so as to overcome said releasable means and drive saidpiston from said retracted position to said travel linzitin7 means, aport in said cylinder adjacent said travel limiting means and disposedjnst below the surface of said piston when said piston has abutted saidtravel limiting means, a reservoir connected to said port, a second portconnected to said reservoir and to a source of air under pressure, avalve for said second port for admitting air under pressure to saidreservoir when said piston abats said travel limiting means, the airunder pressure in said reservoir acting upon the lower surface of saidpiston via said first mentioned port, and a passage from said cylinderfor air beneath said piston when said piston is in its retractedposition, said piston operative when seated on said limiting means bysaid air under pressure to eect a shut-O valve to said passage wherebysaid passage is sealed while air is admitted to said reservoir throughsaid second port, whereby when air pressure is no longer admitted tosaid cylinder and said air pressure is diminished, the air underpressure in said reservoir causes said piston to return to retractedposition where it is held independent of air pressure by said releasablemeans, excess air in said reservoir and cylinder exhausting through saidpassage.

References Cited The following references, cited by the Examiner, are ofrecord in the patented le of this patent, or the original patent.

UNITED STATES PATENTS 1,014,639 1/ 1912 Colwell. 1,465,770 8/1923 Shaft91--5 2,682,052 6/1954 Juilfs. 2,807,021 9/ 1957 Chellis.

FOREIGN PATENTS 1,025,349 9/ 1954 Germany. 1,043,974 .5/ 1959 Germany.

GRANVILLE Y. CUSTER, JR., Primary Examiner.

